platform/1bitsquare_icebreaker: Add possible USB pinouts

The pin outs come from LUNA :
https://github.com/greatscottgadgets/luna/blob/main/luna/gateware/platform/icebreaker.py#L94



and are some commonly used ones from other projects / pmods.

Signed-off-by: Sylvain Munaut <tnt@246tNt.com>